Spring arrangement apparatus for mounting a vibration-sensitive or shock-sensitive device

ABSTRACT

Spring arrangement for mounting a vibration- or shock-sensitive device attached to a supporting member in a housing, with the supporting member being fastened to the housing by helical spring elements. The supporting member is suspended in the housing by helical spring elements so that each elastic force component of one spring applied to the supporting member in a specific direction is counteracted by at least one elastic force component of another spring applied in the opposite direction so that the supporting member remains approximately in the center of the vibration clearance provided regardless of the position in which the housing is mounted in a motor vehicle. Due to the opposing elastic forces of the springs, the spring constant and therefore the natural frequency of the overall system can be advantageously increased, thus avoiding undesired points of resonance at low frequencies.

[0001] The present invention concerns a spring arrangement according tothe preamble of claim 1. A method for attaching a vibration- orshock-sensitive device, such as a stereo system, compact disc player, CDchanger, or floppy or hard disk drive to a supporting member andmounting the supporting member with vibration damping in a housing viahelical spring elements is already known. Particularly in motorvehicles, low-vibration and low-impact methods of attaching compact discplayers are required in order to operate the equipment withoutinterference. For this purpose, the device is thus elastically suspendedon the equipment housing, which is permanently installed in the motorvehicle, with the supporting member being attached to the housing viamultiple helical spring elements provided in the form of eitherextension springs or compression springs. FIG. 1a shows the known springarrangement using extension springs, and FIG. 1b shows the arrangementusing compression springs. In FIG. 1a, a supporting member 2 in the formof a plate, with a compact disc player 1, for example, attached to itstop, is fastened to the top of a cuboid housing 3 via a total of fourhelical springs (10, 11), only two of which are illustrated. Accordingto this arrangement, an excitation acting upon housing 3 produces onlyan extremely diminished acceleration of CD player 1. By suspending thedevice in this manner, points of resonance form which are associatedwith an undesirable, strong vibration of device 1 at low excitationfrequencies, thus causing device 1 to bump against housing 3. To avoidthis disadvantage, it is desirable to increase natural frequency w_(max)of the system subject to vibrations, since this will considerablydiminish the acceleration of CD player 1 during excitation. With a givenmass M according to equation (1), this can be achieved only byincreasing spring constant K. $\begin{matrix}{\omega_{\max} = \sqrt{\frac{K}{M}}} & (1)\end{matrix}$

[0002] However, the supporting plate suspended on springs 10, 11 in FIG.1a must be displaced by the force of its own weight until it ends upmore or less in the center of the vibration clearance provided for it,the height of which is marked x in FIG. 1a. This can be achieved byreducing the spring constant, which, however, should be avoided as shownby equation (1), due to the resulting undesired reduction in the naturalfrequency. The spring arrangements illustrated in FIG. 1a and FIG. 1balso have the disadvantage that they can be used only in situationswhere the springs are loaded axially, i.e., in the direction of thespring axis. However, the springs are more compliant when the force isapplied radially. The springs are barely extended in that case, butrather are merely swivelled or bent. As a result, only weak restoringforces are applied in the radial direction. Radially oriented forces actupon the springs when the device is installed in the motor vehicle in adirection other than the specified mounting position. A situation ofthis type is illustrated in FIG. 2a. When device 3 tilts to the side,supporting member 2 is displaced far to the side by its weight, thusreducing the vibration clearance. If a vibration or impact excitationoccurs, there is the danger of the device striking the side walls of thehousing. The use of a spring arrangement, like the one shown in FIG. 1,is therefore limited to situations in which the compact disc player isspecifically designed for a predetermined mounting position, e.g., if itcan be installed in the vehicle only horizontally or only vertically.Compact disc players in car radio equipment often need to be installedin consoles at an angle. If the player housing is attached to the roofstructure of a bus, for example, a certain angle of inclination isdesirable in order to make the CDS easier to insert. According to therelated art, supporting member 2 is attached to housing 3 in suchsituations, using an additional spring 19 that is adjusted to the angleof inclination. This also has the disadvantage that the CD player can beinstalled in no position in the vehicle other than the predeterminedone. That is why some devices include an adapter mechanism which can beused, for example, to adjust a CD changer to the mounting position athand within certain limits. The known related art is illustrated in FIG.7a and FIG. 7b. FIG. 7a shows the device with its housing 3, initiallymounted in a horizontal position. The CD changer (not illustrated) isattached to a supporting member 2 that is suspended on two discs 40 viatwo springs 10 and 11 so that supporting member 2 is located more orless in the center of the vibration clearance provided for it. Discs 40are each attached to the side walls of device housing 3 so that they canrotate around an axis 41. If the device is installed in a horizontalposition, springs 10 and 11 are located in position A in FIG. 7b. If thesame device is now installed in a vertical position in the motorvehicle, housing 3 is first rotated 90 degrees, and the two discs 40 arerotated 90 degrees in the opposite direction on actuating element 42until springs 10 and 11 are in position B shown in FIG. 7b andsubsequently locked in place. The elastic force of springs 10 and 11compensates for the weight of supporting member 2, along with the devicearranged upon it, so that the supporting member can also vibrate freelyin the housing even when mounted in a vertical position. Anyintermediate positions between 0 and 90 degrees can also be set. Thedisadvantage of this related art is that it requires an expensiveadapter mechanism, which increases the device production costs. Arelatively complicated adjustment of the adapter mechanism to thedifferent mounting positions is also necessary, making it possible toincline the device only around an axis that runs parallel to axes 41.

ADVANTAGES OF THE INVENTION

[0003] The spring arrangement according to the present invention havingthe characterizing features of the main claim has the advantage thatboth the spring constants of the individual springs and the naturalfrequency of the system can be increased. This is achieved by mountingthe supporting member in a predetermined position in the housing. Acomponent of elastic force applied in a specific direction is thenalways counteracted by a component of elastic force in the oppositedirection. This prevents the springs from lifting or lowering thesupporting member too far away from the center of the preset vibrationclearance when using very rigid extension springs or compressionsprings. At the same time, the supporting member can be installed indifferent positions in a motor vehicle without having to adjust thespring arrangement or use an adapter mechanism. Another advantage isthat the position of the supporting member relative to the housingvaries only slightly in different mounting positions, allowing thedevice to be operated without interference independently of the mountingposition when vibrations or shocks occur.

[0004] This is essentially achieved by the fact that the springs notonly swivel or bend when the housing tilts or rotates, as in the case ofthe related art illustrated in FIG. 2a, but rather that, with the springarrangement according to the present invention, the supporting member ismounted in such a way in the housing that the springs are extended whenthe supporting member is displaced in any direction. As a result,restoring forces always counteract the displacement.

[0005] Further advantageous embodiments and refinements of the presentinvention are provided by the features indicated in the subclaims. Forexample, the spring arrangement is advantageously designed so that thesupporting member is arranged more or less in the center of thevibration clearance. This prevents the device from bumping against thehousing at high oscillation amplitudes.

[0006] A further advantage is the use of inexpensive extension springs,the ends of which can be easily attached to the supporting member andhousing and then released again, since this reduces the amount ofinstallation work needed, making it cost-effective.

[0007] A further advantage is to design the supporting member in theform of a flat, rectangular supporting plate. The rectangular supportingplate can be advantageously mounted in a cuboid housing using springsprovided in the corner areas.

[0008] A further advantage is provided by mounting the supporting platein the housing using four extension springs projecting from the platetop and bottom, since this provides stable, elastic mounting of thesupporting plate in the center of the vibration clearance and parallelto the upper and lower housing walls.

[0009] If the supporting plate is attached to the upper housing wall bytwo extension springs in two diagonally facing corner areas of its topand to the lower housing wall by two springs projecting from its bottom,four springs are sufficient in order to mount the supporting plateelastically in the housing. This can reduce the production costs.

[0010] A particular advantage is provided by mounting the supportingplate in the housing with extension springs projecting at an angle fromthe plate and facing away from it. This allows the springs to extendeven farther, with the resulting restoring forces being even stronger,when the device is mounted in an inclined position.

[0011] If the supporting plate is attached to the housing by extensionsprings that are fastened to the longitudinal sides of the supportingplate and oriented more or less parallel to it, an arrangement withthree springs positioned on same plane as the supporting plate issufficient.

[0012] In some situations, e.g., in the case of a CD changer, thevibration-sensitive device is attached to a cuboid supporting member. Insuch situations, the cuboid supporting member is advantageouslysuspended between two opposite side walls of the housing using twotapered springs. The first and last coils of the tapered spring do notcontribute to spring compliance and are advantageously firmly attachedto the side walls in an attachment area lying flat against the sidewalls. The tapered springs allow the supporting member to be mounted inthe housing in a manner that is particularly space-saving andeconomical.

DRAWING

[0013] Embodiments of the present invention are illustrated in thedrawing and explained in greater detail in the following description,where:

[0014]FIG. 1a shows a spring arrangement according to the related artwith a supporting member suspended on extension springs;

[0015]FIG. 1b shows a second spring arrangement according to the relatedart, with the supporting member being mounted on compression springs;

[0016]FIG. 2a shows the spring arrangement in FIG. 1a in which thedevice housing is tilted;

[0017]FIG. 2b shows the spring arrangement in FIG. 2a with an additionalspring adjusted to the tilting angle;

[0018]FIG. 3 shows a first embodiment of the spring arrangementaccording to the present invention for a compact disc player;

[0019]FIG. 4a shows a second embodiment with springs facing away fromthe supporting plate at an angle;

[0020]FIG. 4b shows a diagram of forces for the embodiment illustratedin FIG. 4a;

[0021]FIG. 4c shows a third embodiment with a leg integrally molded ontothe supporting plate;

[0022]FIG. 5 shows one embodiment of the spring arrangement according tothe present invention with four springs;

[0023]FIG. 6 shows a further embodiment with three springs;

[0024]FIG. 7a shows a schematic cross-section of a CD changer accordingto the related art suspended on two springs;

[0025]FIG. 7b shows a side view of FIG. 7a;

[0026]FIG. 8a shows a schematic cross-section of one embodimentaccording to the present invention of the spring arrangement for a CDchanger; and

[0027]FIG. 8b shows a side view of FIG. 8a.

DESCRIPTION OF THE EMBODIMENTS

[0028]FIG. 3 shows a first embodiment of the spring arrangementaccording to the present invention. Vibration- or shock-sensitive device1 in the embodiment illustrated here is a compact disc player. Compactdisc player 1 is located on top 25 of a rectangular supporting plate 2.Supporting plate 2 is attached to top 27 of a cuboid housing 3 by fourhelical spring elements, only two of which are illustrated in FIG. 3,namely springs 10 and 11. Housing 3 is, in this case, shown in ahorizontal mounting position. Inexpensive extension springs made of wirecoiled in a spiral shape, with ends designed in the form of eyes, areused as the helical spring elements. The extension springs allowsupporting plate 2 to be easily installed and removed. The extensionspring eyes are attached to hooks provided in the corner areas ofrectangular supporting plate 2 not covered by CD player 1 and to hookson housing top 27 opposite the first hooks. Bottom 26 of supportingplate 2 is attached in the same manner to housing bottom 28 via fouradditional springs, of which only springs 12 and 13 are illustrated inFIG. 3. The length of the extension springs is selected so that allextension springs attached to housing 3 must extend when they arefastened to the hooks positioned on supporting member 2. After alleight-springs have been attached, supporting plate 2 is mounted inhousing 3. The tensile force of spring 10 applied perpendicular tosupporting plate 2 is counteracted by the tensile force of spring 12,the tensile force of spring 11 is counteracted by the tensile force ofspring 13, etc. Because the spring constant is chosen so that the forcewith which springs 10, 11 provided on the plate top pull the supportingplate toward housing top 27 is the same as the force with which oppositesprings 12, 13 provided on plate bottom 26 pull supporting plate 2toward housing bottom 28, the spring constants, and thus the overallrigidity of the oscillatory system, can be increased without displacingthe supporting plate from the center of the vibration clearance. Thisadvantageously pushes the natural frequency of the overall system towardhigher frequencies. Supporting plate 2 can be connected to housing 3 notonly by the spring elements but also by vibration dampers, which are notillustrated in FIG. 3.

[0029] Furthermore, the weight of supporting plate 2 and device 1 causesonly a slight extension of upper springs 10, 11 and a slight compressionof lower springs 12, 13 with a greater spring constant. In theembodiment illustrated here, therefore, the distance from supportingplate 2 to housing top 27 is slightly greater than the distance tohousing bottom 28. By slightly varying the spring length or adjustingthe points at which the springs are attached to the housing sections, itis possible to position supporting plate 2 exactly in the center of freevibration excursion x, with the plate oriented horizontally at an equaldistance from housing top 27 and housing bottom 28.

[0030] By mounting housing 3 in an inclined position instead of thehorizontal position shown in FIG. 3, supporting plate 2 is displacedparallel to housing bottom 28 by one component of its weight. Thedisplacing weight force acts on springs 10, 11, 12, 13 in the form of aradial force. This is the situation illustrated for the related art inFIG. 2a in which springs 10, 11 swivel or bend. In the springarrangement according to the present invention illustrated in FIG. 3,however, spring 12 prevents spring 10 from merely swiveling, spring 13prevents spring 11 from merely swiveling, etc. Because supporting member2 is mounted in the center of the vibration clearance, all eight springsmust extend when housing 3 tilts and supporting member 2 is displacedlaterally. This extension, in turn, produces a restoring force whichcounteracts the lateral displacement and increases with the springconstant. The lateral displacement is thus much less pronounced than inthe related art. The arrangement also advantageously prevents supportingmember 2 from bumping against the side walls of housing 3 undervibrational load or shocks.

[0031]FIG. 4a shows one refinement of the embodiment illustrated in FIG.3. The eight extension springs, of which only four springs 10, 11, 12,13 facing the observer are shown, project out at an angle from plate top25 and bottom 26 when device 3 is mounted in a horizontal position. Theends of the extension springs not attached to the corner areas ofrectangular supporting plate 2 are fastened to the eight correspondingcorners of cuboid housing 3. This is shown somewhat more clearly in thethree-dimensional representation of FIG. 5, which, however, illustratesonly four springs. It is, of course, also possible to attach the springsto the side walls or fixing elements of a frame instead of directly tothe corners of housing 3. Likewise, it is possible to provide fastenersin the housing and to attach some springs to the fasteners and othersprings to the housing walls. The important thing is only that thesprings are positioned at an angle toward the outside, with the elasticforce component of one spring applied in a specific direction beingcounteracted by an equally strong elastic force component of at leastone other spring. FIG. 4b shows a simplified diagram of forces for theembodiment illustrated in FIG. 4a. To make things simple, therepresentation here is limited to a two-dimensional view. Elastic forcesF₁, F₂, F₃, and F₄ act upon supporting plate 2. Each of these elasticforces, e.g., elastic force F₁, can be broken down into a horizontalcomponent F₁′ and a vertical component F₁′, which is counteracted by anelastic force component of another spring applied in the oppositedirection. For example, component F₁ is counteracted by component F₄′ ofspring 12, and component F₁″ is counteracted by component F₂″ of spring11. Because all forces applied compensate for each other, supportingmember 2 is positioned in the center of the vibration clearance. Theweight of supporting plate 2, which is relatively small compared to thespring forces, merely causes the supporting plate to be slightlydisplaced in the direction of housing bottom 28. The particularadvantage of this embodiment, compared to the example shown in FIG. 3,lies in the fact that the eight springs are pre-tensioned not only inthe horizontal direction, but in the vertical direction as well. Ifhousing 3 is mounted at an angle or even vertically, the inclinedsprings are therefore displaced farther in the axial direction than theyare in the example shown in FIG. 3, which results in stronger restoringforces. In the embodiment shown in FIG. 4a, equally strong restoringforces counteract the displacement of supporting member 2 in anydirection regardless of the mounting position.

[0032]FIG. 4c shows a further embodiment of the present invention.Supporting member 2 in this case is formed by a rectangular plate 2 witha leg 20 integrally molded onto longitudinal side 22 of the plate andprojecting vertically from its bottom 26. Supporting plate 2 is mountedin housing 3 by eight springs, of which only springs 10, 11, 12, and 13are shown in FIG. 4c. The embodiment differs from the example shown inFIG. 4a by the fact that spring 10 is not attached to top 25 of thesupporting plate, but rather to end 29 of leg 20 projecting in thedirection of housing bottom 28, and spring 12 is fastened to edge 22formed by leg 20 and supporting plate 2, so that springs 10 and 11project above top 25 of supporting member 2, while springs 12 and 13project in the opposite direction above bottom 26.

[0033]FIG. 5 shows a refinement of the embodiment illustrated in FIG. 4ain which supporting member 2 is mounted in housing 3 by only fourextension springs 10, 13, 14, 15. Springs 10 and 15 are attached to thesupporting plate in two diagonally facing corner areas of supportingplate 2. Springs 10, 15 project outward at an angle from plate top 25and are attached to housing 3 by their other ends in two cornersdiagonally facing top 27 of housing 3. The other two corner areas ofsupporting plate 2 are attached in the same manner to two otherdiagonally facing corners on bottom 28 of housing 3 via springs 13 and14. The spring arrangement shown in FIG. 5 is therefore based on thespring arrangement in FIG. 4a described above in that four springs arealternately removed from top 25 and bottom 26. However, since restoringforces counteract any displacement of the supporting plate, regardlessof the mounting position, the spring arrangement in FIG. 5 has theadvantage that it requires only four springs.

[0034]FIG. 6 shows a further embodiment of the present invention whichrequires only three springs. Supporting member 2 is suspended like atrampoline in the center of cuboid housing 3 and attached to housing 3by three extension springs 16, 17, 18 arranged on the same plane assupporting plate 2. Extension spring 16 in the corner area formed bylongitudinal sides 21 and 24 of the supporting plate is attached to theinner edge of housing 2 opposite this corner area. In the corner areaformed by longitudinal sides 21 and 24, extension spring 17 is attachedto an adjacent inner edge of housing 3. Third extension spring 18connects the central portion of longitudinal side 23 opposite springs 16and 17 to the center of the housing wall located opposite the inneredges connected to springs 16 and 17. In the embodiment shown in FIG. 6,the distance from supporting plate 2 to the side walls of housing 3 mustbe slightly greater than in the example shown in FIG. 5.

[0035]FIG. 8a and FIG. 8b show a further embodiment of the presentinvention. In this case, the vibration-sensitive device (notillustrated) is a CD changer that is positioned in a cuboid supportingmember 2. Supporting member 2 has at least two side walls 6 and 7 thatare connected to housing 3 by helical spring elements 10 and 11. Used ashelical spring elements 10, 11 are essentially known tapered springswhose inner coils fit together in a spiral shape when the spring isfully compressed, so that the height of the spring, in this case, equalsthe diameter of a single coil. The advantage of tapered springs is thatthey have a low overall height. Tapered springs can be designed as wireor flat spiral springs. In addition, springs 10 and 11 can be providedas extension or compression springs. In the embodiment shown in FIG. 4,springs 10, 11 are designed as extension springs. The springs have, attheir ends, two dummy coils 30 and 31 which do not contribute to springcompliance. End coil 30 of spring 10 is integrally attached to side wall7 of supporting member 2 in an attachment area 33 lying flat againstside wall 7. End coil 31, which has the largest diameter, is integrallyattached to opposite side wall 46 of housing 3 in an attachment area 34.Spring 11 is attached in the same manner to side wall 6 of thesupporting member and to side wall 45 opposite side wall 46 of housing3. In an arrangement with only two springs, the attachment method causesrestoring forces to counteract peripheral forces which result whensupporting member 2 rotates around the axes of springs 10, 11 andproduces torsion in springs 10, 11. The tensile force of spring 10 isalso counteracted by the tensile force of spring 11 so that supportingmember 2 is suspended between tapered springs 10 and 11 approximately inthe center of the vibration clearance provided for it. A high enoughspring constant of the two springs is selected so that the weight ofsupporting member 2, along with the CD changer, produces only a veryslight vertical displacement of supporting member 2. If housing 3rotates around an axis that runs through the longitudinal axis ofsprings 10 and 11, equally strong restoring forces therefore alwayscounteract the weight of supporting member 2, due to the rotationalsymmetry of the tapered springs. In the case of a rotation around anaxis running perpendicularly to the paper plane in FIG. 8a, strongrestoring forces also counteract the horizontal displacement ofsupporting member 2, unlike the related art illustrated in FIG. 7a, sothat supporting member 2 continues to remain more or less in the centerof the vibration clearance.

1. Spring arrangement for mounting a vibration- or shock-sensitivedevice (1) attached to a supporting member (2) in a housing (3), withthe supporting member (2) provided in the form of a supporting platewith a top (25) and a bottom (26) and suspended in the housing (3) byhelical spring elements (10-19) so that each elastic force component ofthe one spring applied to the supporting member (2) in a specificdirection is counteracted by at least one elastic force component ofanother spring applied in the opposite direction, characterized in thatthe supporting member (2) is mounted in the housing by four extensionsprings, the ends of which are designed in the shape of eyes, hooks, orcorresponding fasteners, with two extension springs (10, 15), located inopposite areas of the supporting plate (2), projecting from the platetop (25) and attached to at least one first housing section, and withtwo additional extension springs (13, 14), located in two other oppositeareas of the supporting plate (2), projecting from the plate bottom (26)and attached to at least one second housing section opposite the firsthousing section, with the supporting plate (2) being held by theextension springs at more or less the same distance from the first andsecond housing sections (FIG. 5).
 2. Spring arrangement according toclaim 1, characterized in that the supporting member (2) is locatedapproximately in the center of the vibration clearance provided for it.3. Spring arrangement according to claim 1, characterized in that thesupporting plate (2) is attached to the housing (3) by extension springsprojecting at an angle from the supporting plate and facing away fromit.
 4. Spring arrangement for mounting a vibration- or shock-sensitivedevice (1) attached to a supporting member (2) in a housing (3), withthe supporting member (2) being suspended in the housing (3) by helicalspring elements (10-19) so that each elastic force component of onespring applied to the supporting member (2) in a specific direction iscounteracted by at least one elastic force component of another springapplied in the opposite direction, characterized in that at least twotapered springs (10, 11) acting in opposite directions are provided asspring elements, with one end (30) of each spring being attached to aside wall (6, 7) provided on the supporting member (2) and the other end(34) attached to a side wall (45, 46) of the housing; and the end coils(30, 31) of the tapered springs (10, 11) are dummy coils which do notcontribute to spring compliance, one end coil being connected to theside wall (6, 7) of the supporting member (2) and the other end coilbeing connected to the side wall (45, 46) of the housing (3) inattachment areas (33, 34) lying flat against the side walls (FIG. 8a).